This invention relates generally to a detonator system and particularly is concerned with a two-wire system which can be operated in a daisy chain fashion.
The cost of electrical conductors constitutes a significant component in the overall cost of a detonating system. It should be borne in mind that the prospect of recovering a conductor from a blast site is, at best, remote. It is therefore desirable to be able to reduce the quantity of electrical conductors used in a blasting system.
A plurality of detonators can be interconnected to one another in a so-called daisy chain configuration. In this arrangement detonators are addressed sequentially and communication with a first detonator is then followed by communication with a second, succeeding detonator, and so on. Typically a daisy chain configuration requires a four-wire detonator harness and the individual detonators are successively connected to a three-or-four-wire surface harness to make up a desired blast configuration.
The specification of PCT/AU2006/000315 describes an electronic blasting system in which detonators are connected to a surface harness by two-wire leads and wherein an actuator is positioned between adjacent detonators. In its simplest form the actuator is a switch and is operable in response to an appropriate command signal. This means that the actuator must possess the capability to identify, and then respond to, the command signal which may be one of a plurality of possible signals.
A similar approach is disclosed in the specification of U.S. Pat. No. 4,846,066. This document discloses detonators which are connected in such a way that programming signals will only be received by a given detonator when an adjacent detonator, nearer to a signal output, has been programmed. This is achieved by making use of a connector which is associated with each detonator. The connector includes a switching device which is operated by a logic element. Signals can only pass beyond a connector when a detonator associated with the connector has been programmed.
The present invention aims to provide a detonator system in which the need for a logic element in the connector is eliminated.